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January 24, 2005 NOA Project Number: E04158A i should be based on the On-Site Wastewater Disposal Standards or other engineering recommendations. L 4.0 GROUND WATER INFORMATION 4.1 Ground Water Depth and Gradient The San Joaquin County Flood Control and Water Conservation District (1998 and 1999) ground water depth and elevation maps were reviewed to determine the ground water levels near the Site. The Fall 1998 and Spring 1999 maps are the most current official maps available from the County. According to these maps (Plates 3-6),ground water occurs at about 59 feet below ground surface, and the groundwater gradient slopes toward the northwest at and flows at a gradient of about 10 feet per mile in the vicinity of the Site. ism No ground water was encountered by the staff of Neil O.Anderson&Associates, Inc. during the drilling of the deep percolation test holes to a depth of approximately 25 feet on January 20, 2005. 4.2 Potential Ground Water Contamination Issues ILIdentifying potential ground-water contamination sources was not part of the scope of work for the soil suitability study. In general,potential ground-water contamination can occur from any number of sources which often include leaky underground storage tanks, agricultural activities,dairies, septic Lsystems,and storm water infiltration. Any past agricultural activities and the present use of septic systems in the area should be considered potential ground-water contamination sources. LA Surface and Subsurface Contamination Report (NOA,2004) addressed the issue of potential contaminant sources. Please refer to this report for further details.At the direction of San Joaquin County EHD,a water samples was collected from the on-site well on May 20,2004 and was analyzed by Cyanazine by EPA Method 252.2 and for MCPAby EPA Method 8151A. Neither compound occurred at a concentration above analytical detection limits. L4.3 Water Sample Location One well permit was found for the subject property (28567 East Highway 120) during file review conducted at EHD on January 6,2005. This 1978 permit was for the installation of a new domestic well completed at 160 feet deep. An existing well was indicated on the site plan to be located 50 feet south of the new well. LAs part of the current investigation,a water sample was collected from the exterior tap on the front of the existing residential structure after purging the tap for a minimum of 10 minutes. L4.4 Water Sample Constituents The water sample was analyzed for nitrate and 1,2 Dibromo-3-chloropropane (DBCP) by EPA ion 5 .444,,,